The present invention relates to a lens actuating device and an image pickup apparatus and, more particularly, to the art of moving a movable lens based on the displacement of a working fluid that is caused when a piezoelectric device is deformed, so that the movable lens can be moved an increased distance with a reduced electric power consumption.
Lens actuating devices for moving a movable lens in predetermined directions are incorporated in video cameras, still cameras, and various image pickup apparatus including cellular phones, etc. The movable lens and a lens holder by which the movable lens is held jointly make up a movable unit, which is moved by the lens actuating device in the directions of the optical axis for focusing or zooming and also in directions perpendicular to the optical axis for correcting image blurs.
Some lens actuating devices have a linear actuator including an actuating coil, an actuating magnet, etc. For details, reference should be made to Japanese Patent No. 3387173, for example.
However, because of the components of the linear actuator, the lens actuating devices with the linear actuator are structurally complex, require a large installation space, and make the image pickup apparatus large in size.
Another problem is that those lens actuating devices have a large electric power requirement because the actuating coil needs to be energized at all times for keeping the movable unit in a desired position as well as moving the movable unit in its movable range.
Another lens actuating device employs a piezoelectric device that is elastically deformable when subjected to an externally applied voltage. For details, reference should be made to Japanese Patent Laid-open No. 2000-194026, for example. The piezoelectric device consumes a small amount of electric power and is small in size and weight.
However, the amount of deformation, or the amount of displacement, which the piezoelectric device produces when a voltage is applied thereto, is very small. If it is necessary to move the movable lens a large distance by the optical design, then a high voltage needs to be applied to the piezoelectric device or the piezoelectric device needs to be an increased length. As a result, the lens actuating device requires large electric power consumption or the image pickup apparatus becomes large in size.